Relaxation dynamics of rubbed polystyrene thin films

Optical retardation measurements were used to probe the chain relaxation dy namics in rubbed polystyrene films of varying thicknesses on glass substrat es. A model based on Kohlrausch-Williams-Watts relaxation was developed and used to determine the glass transition temperature (T-g) Of the films. Res ults showed reductions of 15-20 K in T-g for thin films of thicknesses comp arable to the radius of gyration as well as for cast films rubbed with diff erent strengths. These results provide evidence of a faster relaxation dyna mics relative to the polymer-substrate interface for thinner films and enha nced chain mobility at the polymer-air interface.